Category: General Navigation

Grid Navigation Introduction to Grid Navigation Grid navigation helps in avoiding the steering problems at high latitudes True or magnetic directions are unusable in in high latitudes due to 3 reasons Rapid convergence causes true track to change rapidly Magnetic variation is high and varies considerably Magnetic compass is ineffective due to lesser horizontal component Grid Charts Grid charts are created by nominating a datum meridian and calculating directions throughout the chart with the datum meridian Grid charts have a square grid instead of latitude longitude graticules Grid charts are…

Sunrise & Sunset Sunrise and Sunset The tilt of spin axis of the earth with the orbital plane results in seasonal variation in duration of daylight The time of sunrise and sunset are affected by certain factors A combination of Sun’s Declination and observer’s latitude affects the duration of daylight Semi-diameter or radius of the sun also affects sunrise and sunset Refraction of light in the atmosphere increases daylight time Effect of Sun’s Declination on Sunrise and Sunset Declination of the sun affects the time of sunrise and sunset Consider…

Measurement of Time Hour Angle Hour angle is the arc of the equinoctial which is equivalent of longitude Hour angle is measured westwards from 0° to 360° between datum meridian and meridian of celestial body Hour angle varies constantly due to rotation of earth Hour angle is 000 degrees, when the celestial body transits a given meridian When the body transits the anti-meridian, its hour angle is 180 degrees Greenwich and Local Hour Angles Hour angles are called either Greenwich or Local hour angles based on the selected datum meridian…